1. Field of the Invention
The present invention relates to a two-dimensional optical waveguide apparatus, and an opto-electronic hybrid circuit board that includes an electronic circuit layer and an optical circuit layer in a hybrid form.
2. Description of the Related Background Art
In recent years, cellular phones and personal digital assistants (PDAs) have been more and more widely used drastically, and equipment with smaller size, lighter weight and higher performance is desired. However, operation speed and integration of electronic circuit boards increase as the size and weight of equipment are reduced and the performance of equipment is enhanced. Accordingly, appropriate and prompt measures are strongly needed to cope with malfunctions of equipment due to signal delay and electromagnetic interference (EMI). In such a situation, the optical circuit or interconnection is expected to radically solve the above technical problems. The optical circuit or interconnection can reduce the EMI radiated from the wiring, and can transmit optical information at high speed.
Japanese Patent Application Laid-Open No. 9(1997)-96746 discloses the following optical circuit board which makes use of the technical advantage of the optical wiring. In this optical circuit board, an optical wiring portion and an electronic wiring portion are separated from each other, optical switches or optical modulators provided on the board are driven by a voltage signal supplied from electronic equipment, and light propagating through optical waveguides provided on the substrate is modulated. The electrical signal is thus converted into an optical signal, and transmitted. The thus-transmitted optical signal is again converted into an electrical signal by a light-receiving device provided on the board, or another board, and the signal is transmitted to another piece of electronic equipment, or the same electronic equipment. In this construction, the electronic wiring is partly replaced by the optical wiring, but places for executing electrical/optical (EO) signal conversion or optical/electrical (OE) signal conversion are limited since the optical wiring path is comprised of a transmission line (i.e., a line-shaped linear polymer waveguide).
Further, Japanese Patent Application Laid-Open No. 2000-199827 discloses an apparatus wherein a 45-degree mirror is used to couple light, which enters or emerges perpendicularly, to the optical waveguide. The 45-degree mirror is thus used to couple light to the waveguide, or couple light transmitted in the waveguide to a light receiving device, and hence the transmission path is inevitably a linear path. Accordingly, when plural transmission paths are to be formed, places where light emitting devices and light receiving devices are situated are limited. Flexibility of board designing is thus small.